1. Field of the Invention
The present invention relates to an improvement of a general-purpose engine fuel tank fuel vapor treatment system, the system including a canister mounted on a peripheral part of a fuel filler opening of a fuel tank mounted on a general-purpose engine, the canister housing a fuel adsorbent for adsorbing fuel vapor generated in the interior of the fuel tank.
2. The Related Art
Such a general-purpose engine fuel tank fuel vapor treatment system is already known, as disclosed in, for example, Japanese Patent Application Laid-open No. 7-34985.
In such a conventional general-purpose engine fuel tank fuel vapor treatment system, a canister is formed from part of a tank cap fitted into a fuel filler opening of a fuel tank, an outer end of an air vent of the tank cap is connected to a downstream chamber of an air cleaner of the engine via a pipe, and fuel vapor that cannot be absorbed by a fuel adsorbent within the canister is taken in by the engine.
However, in such a conventional system, it is necessary to provide troublesome piping between the tank cap and the air cleaner; not only does the cost increase, but also the intake negative pressure of the engine acts to some extent on the interior of the fuel tank when the engine is running, and there is therefore a possibility that, due to variation in the intake negative pressure, the characteristics of fuel supply from the fuel tank to the engine might become unstable.